The invention relates to centrifugal pumps and more particularly to centrifugal pumps with dynamic seal and static seal arrangements.
A dynamic seal arrangement uses one or more auxiliary impellers in a centrifugal pump. As pumped fluid enters the dynamic seal stuffing box cavity, it is opposed by centrifugal force generated by the auxiliary impellers which prevent leakage of the fluid along the impeller shaft. When the pump is not operating, a static seal adjacent to the dynamic seal acts to prevent leakage in a known manner.
The number of dynamic seal stages depends of course on the stuffing box pressure, operating speed, and diameter of the auxiliary impeller. A conventional centrifugal pump has limited space between the inboard bearing and the pump impeller. Therefore, for many applications, dynamic seals with two or more stages cannot be used.
Another problem with such arrangements is to protect the static seal from contaminants. This becomes very critical and difficult for pumps used in applications where a high percentage of solids are present in the fluid being pumped.